The present invention is with respect to storage bags and more specially to such bags for medical purposes for the storing of blood or infusion solutions and made up of a thermoplastic polymeric material with at least one hose-like outlet.
Bags of this sort are used on a very large scale for medical purposes so that the overall number of bags used is of the order of millions. The bags are needed for example for taking up blood as a blood storage bag or for the sterile storage of solutions for parenteral injection solutions. For this purpose the bags have to be completely sterile and to this end normally have to be heated to at least 100 degrees C. or more specially about 120 degrees C. Even for this purpose the thermoplastic polymeric material has to have such properties that it is thermally stable, at least up to the temperature to which it is heated for sterilization.
Further properties desired of such bags are that they be light in weight, low in price and able to be produced automatically, while furthermore their value after use is to be so low that they may in good conscience be thrown away. Moreover the material of the bag is to be flexible, able to be folded and, in the processed condition so glass-clear that it is possible to see at once if there have been any undesired changes in the liquid stored in the bag.
The only polymer that so far has kept to this specification of desired properties is flexible vinyl, that is to say plasticized polyvinyl chloride (PVC) or polyvinyl chloride with the addition of plasticizers in order to get better elastic properties. Such plasticizers or softeners, as for example diisooctyl phthalate are however the cause of some undesired effects. In point of fact such plasticizers are not completely locked in the spaces between the polymer chains and may be leached out by the water or aqueous solution from the polymer so that there is a contamination of the liquid stored in the bag.
It has been roughly worked out that a patient treated for some time with solutions from such bags made of flexible vinyl will take up one gram of plasticizers in his body, that is likely to be the cause of long term physiological damage to the patient.
Moreover, if made of flexible vinyl, a bag is likely to be attacked by microorganisms, that more specially will be responsible for leaching of the plasticizer and for this reason general destruction of the bag. In this respect such a bag of flexible vinyl after filling has to be safeguarded by a special outer packaging structure to keep out such microorganism.
These facts in connection with such flexible vinyl bags have made it impossible for them to take the place of glass bottles, as have been normally used to date, on any wide scale. In fact, in some industrialized countries public authorities have not allowed the use of vinyl bags for medical purposes at all.
For this reason tests were undertaken on other materials with a view to coming across one that might be used in place of flexible vinyl, but all the materials tested were overhigh in price or did not have the desired mechanical and physiological properties. For example one tested material had an overly high permeability to water vapor so that, if used, there would have been an undesired increase in the concentration of materials in a solution stored therein. Further undesired properties of the materials were the presence therein of substances that were readily leached out, or damage on rough handling of the bags.
The Swiss Pat. No. 444,382 has an account of such a plastic bag, that may be used for therapeutic liquids for parenteral administration. The wall of this plastic bag is made of a resin laminate, that on the outer side, that is to say the side facing away from the liquid, has a flexible vinyl layer and on the inner side has a polyhalogen hydrocarbon synthetic resin layer. This last-named layer is free of any substances that are undesired from the pharmacological point of view and that might be leached out into the solution stored in the bag. However such polyhalogen hydrocarbons as used do have the undesired property of being high in price with respect to manufacturing and processing and furthermore of not fusing to the desired degree on making welded seams so that there is in fact still direct contact with the flexible vinyl. Such undesired direct contact is furthermore to be seen at the outlet opening structure that is normally made completely of flexible vinyl and may be joined up with further connection hose of flexible vinyl. Moreover such a throw-away or disposable bag has undesired effects on the environment inasfar as when the bag material is burned hydrogen halides, that are strong chemicals, are let off into the atmosphere.
A further bag is to be seen in the U.S. Pat. No. 4,140,162 which is made up of a resin composition with three components. These components are a polyolefin, that is by and large made up of propylene unit only, a block copolymer and if needed a plasticizer, that may as well be a polymer. As further components of the bag antioxidants may be used, that may hardly be thought of as hygienic and healthy additions.
It will be clear from the observations made herein so far on possible components that not only the components as such but furthermore the processing thereof are high in price and that a bag or recipient made of such materials is hardly likely to be in the position of taking the place of normal flexible vinyl bags, this being for reasons of price and of process engineering.
It is for this reason that the present assignee herein has made a German patent application (see German Offenlegungsschrift specification No. 3,026,974) covering a further plastic or resin composition for producing connection elements for joining vinyl hose to polyolefin bags. This plastic composition is again made up of a number of polymeric components, that from the point of view of manufacturing technology and price are not any better than the components taken into account so far. Furthermore this connection element has to be able to be welded not only to the polyolefin bag but furthermore to the flexible vinyl hose, an operation that would normally be high in price and not readily undertaken.
The special point to be kept in mind in connection with the suggestions of the prior art is that in every case a flexible vinyl connection hose is used, that by its very nature has a plasticizer and is a danger to health.
Such connection hose, that is normally welded to the flexible vinyl bags as an outlet nipple or spout, has the desired highly elastic properties necessary if the plug-on end connectors are to be kept in place and there is to be no chance of the liquid stored in the bag running out between the stopper and nipple on sterilization at about 120 degrees C. A further point is that the stopper has to be so firmly gripped in the piece of hose round it that it may only be pulled out of it using a strong pulling force.
Another point to be kept in mind is that in the food products industry flexible plastic bags have long been in use, which in some cases have had a welded on outlet spout made of the same material as the rest of the bag. Such outlet structures do however not have the highly elastic properties as noted hereinbefore and for this reason may only be sterilized if the bag as such is able to be sterilized.